Process for the production of fertilizers



April 18, 1939. H. A. BEEKHUIS. JR 2,155,372

PROCESS FOR THE PRODUCTION OF FERTILIZERS Original Filed March 10, 1951L /9 fvcf/an Fan my INVENTOR m I Herman A. Beef/1MB" Jr ATTORN EYPatented Apr. 18, 1939 rnocEss ron. ran raonuc'non or marmzsas Herman A.Beekhuis, in, Petersburg, Va... as-

signor, by mesne assignments, to The Solvay Process Company, New York,N. Y., a corporation of New York Application March 10,

1931, Serial No. 521,482

Renewed April 10, 1937 2 Claims.

This invention relates to a process and apparatus for the production offertilizers. More particularly, this invention relates to the productionof a fertilizer in granular form contain- 5 ing ammonium nitrate andcalcium carbonate and methods for their production.

It has heretofore been proposed to prepare a fertilizer by admixingcrystalline ammonium nitrate with the calcium carbonate residues ch- 10tained in the production of ammonium sulfate by reaction of calciumsulfate in suspension in water with ammonia and carbon dioxide. Theprecipitated calcium carbonate formed as the result of this reaction isseparated from the solu- 15 tion of ammonium sulfate and is admixed withthe ammonium nitrate crystals. It has also been proposed heretofore toprepare granular fertilizers by allowing a hot concentrated solution orfusion of a fertilizer salt to cool while falling 20 freely through agaseous atmosphere. The dispersed fluid is solidified during its fallthrough the gas and a product consisting of more or less regulargranules is obtained.

It is an object of this invention to provide a 25 process for theproduction of a granular fertilizer comprising an intimate admixture ofammonium nitrate and finely divided calcium carbonate. Further, it is anobject of this invention to provide an apparatus for the production of afertilizer comprising ammonium nitrate and calcium carbonate in granularform. Other objects of the invention will in part be obvious and will inpart appear hereinafter.

I have discovered that a granular fertilizer 35 having satisfactoryphysical characteristics may be prepared by dispersing a concentratedsolution of ammonium nitrate containing finely divided calcium carbonateinto an atmosphere of a cooling gas.

In carrying out the process of this invention, a concentrated solutionof ammonium nitrate containing suspended finely divided calciumcarbonate, heated to a temperature at which the mixture is fluid, isdispersed as separate parti- 45 cles into an atmosphere of an inert gashaving a temperature below the solidification temperature of themixture. The particles are allowed to pass freely through the gas untilthey are sufficiently solidified to retain their shape upon be- 50 ingcollected and to permit of their being fed to a drier wherein thesolidified particles are dried. In its preferred embodiment, thisinvention comprises the addition of finely divided calcium carbonate toabout a 90% ammonium nitrate solu- 55 tion at a temperature of aboutoo-r20 g, The

mixture is fed to a revolving disc from which it is dispersed into abody of air at about atmospheric temperature. The dispersed particlesare cooled by falling through the air and are collected and immediatelyfed into a rotary drier. In the drier, the particles are treated withair heated to 12 C. while being agitated to prevent the granules fromsticking together.

The invention accordingly comprises the several steps and the relationof one or more of such steps with respect to each of the others and theproduct possessing the features, properties and the relation ofconstituents which are examplified in the following detailed disclosureand the scope of the invention will be indicated in the claims. I

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawing in which:

The numeral l indicates a vessel provided with a stirrer 2. Vessel l isarranged for heating by means of steam introduced into a space 3provided in.a steam jacket 4 about vessel i. The bottom of vessel l isprovided with a delivery spout 5 and trough Ill. The entrance to spout 5may be opened or closed as desired by means of a valve 6. Below vessel lis positioned a disc I connected by a spindle 8 with a motor, not shown,whereby disc i may be rapidly rotated. A funnel 9 surrounds spindle 8and is positioned to guide a fluid flowing from trough ill to the centerof rotating disc 1. Below disc 1 there is a collecting hopper ii which,in the apparatus shown, takes the form of an inverted cone provided atits apex with a delivery tube ii. The sides of collecting hopper ii areat such an angle with the horizontal that a solid material fallingthereon moves under the influence of gravity toward and through deliverytube i2, below which is positioned a funnel IS, the delivery tube ofwhich opens into a rotary drier [4. The walls of collecting hopper llmay be provided with a jacket 20 which forms a space 2i between thewalls of the hopper and the jacket. If desired, a warming fluid, forexample warmed air, may be circulated through the space within jacket 20from an inlet 22 to an outlet 23 to warm the walls of collecting hopperII. An air heater [5 containing steam coils i6 serves to warm air drawnthrough the heater and drier it by means of an exhaust fan ii. Theexhaust gas passes from fan I! through a dust collector l8 and thence isdischarged to the atmosphere. The

material treated inthe drier leaves the samethrough a discharge is andmay be cooled and packed for shipm nt.

The following examples are representative of processes which may becarried out employing the apparatus described above:

Example I.A. 90% ammonium nitrate solution is added to vessel -l andheated to a temperature of 100-105 C. by means of steam passed intojacket 4. Finely divided calcium'carbonate is added to the ammoniumnitrate solution in the proportion of about lbs. of the calciumcarbonate to every 100 lbs. of the ammonium nitrate solution and'themixture stirred to maintain the calcium carbonate in suspension in thesolution. The mixture at 100-105 C. is allowed to fiow past deliveryvalve 8 through spout '5 and trough It to the center of rotating disc Iwhich throws the mixture outwardly therefrom in the form of more or lessspherical particles. These spheres are allowed to fall through air orother inert gas for such a distance that they are sufficientlysolidified to retain their shape on striking collecting hopper II. Thesolidified pebbles pass downwardly along the sides of the-collectinghopper through delivery tube l2 and funnel l3 into the rotary drier llwhere they are dried by heated air drawn through heater IS. The productleaving discharge I! may contain not more than about 0.25% moisture. 7

It has been found that the pebbled material has a tendency while beingdried to adhere to the walls of rotary drier II and to form a smallamount of relatively large lumps. These larger lumps may be removed byscreening the product delivered from the rotary drier. This tendency ofthe material to cake during drying and toadhere to the sides of therotary drier may be materially lessened by introducing calcium carbonatedust, for example, pulverized limestone, with the air drawn throughdrier ll. The dust which leaves the drier with the air is recovered indust collector 18;

Example II.A mixture of ammonium nitrate solution and finely dividedcalcium carbonate in proportions of about 150 lbs. calcium carbonate toevery 100 lbs. of ammonium nitrate solution is prepared and heated invessel I as described in Example 1 above. The mixture at about 100-105"C. is fed'at a uniform rate to the center of disc I. This disc, forexample, may have a diameter of six inches and be rotated at a speed ofabout 765 revolutions per minute. The mixture is thrown from the disc inthe form of separate particles which are allowed to harden by fallingthrough air for a distance of about 40 feet to collecting hopper II.'The hardened particles pass from the collecting hopper to rotary drierll where they are treated in the manner described in Example I.

Example III.A mixture of ammonium nitrate and finely divided calciumcarbonate is prepared by adding the calcium carbonate to about aammonium nitrate solution at a temperature of the temperature in thedrier at the end to which the pebbled material is fed does not exceedabout C. as otherwise there is a tendency for the pebbles todisintegrate.

The rotating disc and collecting hopper employed in carrying out theprocess of this invention may be placed in a large room withoutparticular provision being made to maintain a current of air flowingcounter-current to the falling particles of the material. If desired,however, a counter-current of air or other gas inert to the materialbeing treated may be circulated in con tact therewith. If atmosphericconditions make it necessary or desirable to adjust the water vaporcontent of the air or its temperature, air properly conditioned withrespect thereto may be circulated into the zone of falling particles. Ithas been found that when the humidity of the air through which thedispersed particles fall is relatively high, for example above about'6080%, there is a tendency for the particles tostick to the sides ofthe collecting hopper. This sticking may be prevented by conditioningthe air. It has likewise been found that the sticking of the particlesto the collecting hopper may be obviated by warming the collectinghopper. For this purpose, a fluid at a desired temperature may beintroduced into jacket 20 shown in the apparatus of the drawing andcirculated in the space therein about the sides of the collecting hopperto warm it to a temperature at which the granules do not adhere thereto.The mixture of ammonium nitrate and calcium carbonate may be dispersedinto the cooling gas 'at lower temperatures than 100? C., but lowertemperatures are not preferred as both the moisture content of the meltand length of fall of the droplets should then be increased in order tomaintain the slurry sufiiciently fluid for dispersion employing thepreferred form of the apparatus and to permit the, dispersed fluid tosolidify sufllciently before striking the walls of the collectinghopper. With other forms or types of spraying apparatus, however, it maybe desirable to disperse the materials at a lower temperature than 100C. and this invention is not limited to the particular details ofoperation set forth above. A temperature materially above inert toammonium nitrate, such as finely ground sand, may be employed either inaddition to or as a substitute for calcium carbonate in the productionof fertilizers in accordance with the process described above. Calciumcarbonate, however, is preferred as it is a soil conditioner, and I havefound it advantageous to use the calcium carbonate formed in theproduction of ammonium chloride from calcium chloride, ammonia andcarbon dioxide.

Since certain changes in carrying out the above process and certainmodifications in the composition which embody th invention and in theapparatus, for practicing the principle thereof may be made withoutdeparting from its scope, it is intended that all matter contained inthe above description or shown in the accompanying drawing shall beinterpreted as illustrative and aisas'la not in a limiting sense. Thefertiliser product described may be admixed with other ingredients ifdesired or may be applied alone to the sofl.

In my copending application Serial No. 729,087

-I also describe and claim as my invention the 91'0- iizer whichcomprises preparing a fluid mixture containing ammonium nitrate and aninert solid in finely divided form, dispersing said fluid mix ture inthe form of separate particles into a cooling gas, solidifying saidparticles during their travel through said gas, allowing said particlesto tail upon the sides of a collecting hoppe removing the solidparticles from said collecting hopper to a dryer, and warming the wallsof the collecting hopper.

2. The process of producing a granular tertilizer which comprisespreparing a fluid mixture containing ammonium nitrate and finely dividedcalcium carbonate, dispersing said fluid mixture in the form of separateparticles into a cooling gas, solidifying said particles during theirtravel through said gas, allowing said particles to fall uponvthe sidesof a collecting hopper. removing the solid particles from saidcollecting hopper to a dryer, and-warming the walls of the collectinghopper.

HERMAN A. Jr.

